Photographic means for recording sound



March 30 1926. 1,578,514

R. HART PHOTOGRAPHIC MEANS FOR RECORDING SOUND Filed May 18, 1925UUUUUUU ll g. .17.

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Patented Mar. 30, 1926.

I z RUSSELL HART, OF LOS ANGELES, CALIFORNIA.

PHOTOGBAPHIG MEANS FOR RECORDING SOUND.

Application filed-May 1a, 1925. Serial No. 31,251.

To all whom it may concern:

Be it known that I, RUSSELL HART, a citi- E zen of the United States,residing at Los Angeles, in the county of Los Angeles and State ofCalifornia, have invented a new and useful Photographic MeansfonRecording Sound, of which a specification is set forth below. I

In this specification, and the accompanying drawing, I shall describeand show a pre ferred form of my invention, and specifical- 1y mentioncertain of its more important objects. I do not limit myself to theforms disclosed, since Various changes and adaptations may be madetherein without departing from the essence of .my lnvention ashereinafter claimed; and objects and advantages, other than thosespecifically mentioned, are included within its scope.

My invention relates to photographic.

means for recording sound and its principal objects are; first, toprovide means for pro- I jecting an exceedingly thin beam of actinicrays upon a movable photo-sensitized film; second, to afford facilitiesfor vibrating the beam telephonically so as to produce a continuoussound record upon the film when the latter is given a uniform motion;and, third, to accomplisli the above by means of apparatus of greatsimplicity.

My objects are attained in the manner illustrated in the accompanyingdrawings, in which Figure 1 is a fragmentary plan view of one form of myinvention, in which certain parts are shown in section;

Figure 2 is an elevation of the above construction,'shown partly insection and with a portion of the camera box removed;

Figure 3 is an elevation of a short section of film on which a soundrecord has been recorded in the manner to be described hereafter; and

Figure 4 is an elevation of a satisfactory type of light' source for usein connection with my invention.

Similar reference numerals refer to similar parts throughout the severalviews.

Myapparatus comprises a suitable base 5 adapted for mounting on a camerain any convenient manner as by a bracket and screw holes 6. Upon anextension of the base is mounted a relatively large sprocket drum 7 withsprockets 8 adapted for engaging a moving picture film There are also apair bf rollers 10 for guiding the film. These parts are all withinalight-proof camera box of which a portion of the wall is shown at 11.Outside of the camera. box is a magnet 12 which may be either apermanent magnet or an electro-magnet, as indicated in Fig. 2.

This magnet has opposed bifurcated poles,

the opposed faces of which are slightly spaced. In the form depicted onepair of the pole branches 13 and 14 are integral with the magnet frame.The other pair of pole.

branches 15 and 16 are adjustable by means of screws 17 so that the gapbetween their faces may be varied. Inthis manner it is ossible tocompensate for the different engths of the magnetic circuits through thepole bifurcations, so that approximately the same magnetic flux may bemade to pass between each pair of pole faces. That is to say,

the flux through the gap between poles 13 and 14: may be made to closelyapproximate the flux through the gap between pole faces 15 and 16. Incertain cases it may be advisa ble to make the poles of both pairs ofbifurcations adjustable.

A small cylindrical armature 18, intermediately. pivoted at 19, ismounted cen trally in such a manner that its extremities are in therespective magnetic fields of the bifurcated magnet poles. This armaturecarries a small cylindrical mirror 20 coaxially mounted upon its upperextremity. The purpose of this mirror will be explained presently.

Surrounding the armature in an energizinm coil 21 adapted by means ofits termina wires 22 to be connected into a telephonic circuit.

It will be noted that the two pole bifurcations on each side of thearmature are of the same polarity. That is, both pole bifurcations onthe left are either north or south and on the right are either south ornorth. When coil 21 is energized one pole of the armature becomes northand the other south and therefore the magnetic attractions of thebifurcated poles cooperate in causing it to swing about its pivot.Changes and reversals of current in coil 21 obviously cause the armatureto vibrate in consonance therewith at variable frequency and amplitudecorresponding in the characteristics of the telephonic current.

The armature is prevented from contacting with the pole faces by meansof resilient material 23 crowded in between the armature and one or bothpairs of pole faces- This material also damps the armature movements ina manner that has been found in practice to be highly desirable forsound recording. I have found that sponge rubber is an excellentmaterial to use for this in a bracket 25 and extending through wall 11of the camera box. This tube is longitudinally slidable so that asecondary image of a primary image thrown upon the mirror, may befocused by means of lenses 26 upon the film in a direction normal to itssurface. The set screw 27 maintains the focus when the adjustment iscomplete.

' For the light source I prefer to employ a lamp of the type shown at 28having a th1n rectilinear filament 29 and mounted vertically in anyconvenient manner as by means of base 30. If a lamp of this character ispo s1- tioned approximately as shown in 1, its rays 31 will fall uponcylindrical mirror 20 and be reflected in the form of a much attenuatedprimary image 1n the d1rect1on of lenses 26. The latter may be made tofocus a sharp secondary image, which may be further attenuated, upon thefilm at 32. In this manner the actinic rays falling upon the film aremade to take theform of an exceedingly thin beam of light which 1s v1-bratile in the direction of motion of the film. Vibratory movements ofthe arma ture and mirror therefore may be made to expose a longitudinalstrip upon the moving film and if the movement of the film is uniform,and the vibrations are produced tele phonically, the film when developedwill show a sound record of the character shown at 33 in Fig- 3.

The sound record comprises a series of variably spaced parallel lines ofvar1able density. The spaces between the lines are also slightly exposedand of variable density. 'For reproduction of the recorded sound thefilmis made to pass at a uniform s eed, corresponding to the recordingspec in front of a suitable photo-electric cell and a tenuous beam oflight is caused to pass through the record and impinge upon the cell.There are various known means for reproduction in this manner and thereproduction is not a part of the present invention and not claimedherein.

The film is preferably driven at a uniform velocityby means of thesprocket drum 7 and the latter is relatively largeand fairly heavy sothat its inertia may exert an appreciable effect in maintaining auniform motion of the film during the recording. This arrangement is farbetter than running the film through an exposure gate for the reasonthat it completely eliminates chattering or vibration of the film byreason of its being pulled through such gate. Vibrations of thischaracter of course produce stray noises and injure the quality of thesound record. Moreover the large sprocket drum 7 accurately positionsthe film during the recording process. 1

Having thus fully described my invention in a manner that will be clearto those familiar with the art concerned, I claim: v

v 1. Photographic sound recording means comprising; a uniformly moveablephoto- 'sensitized film; a light source; and a cylindrical mirror,vibratile to sound, whereby an attenuated image of said source may bethrown upon said film transversely to its direction of motion.

2. Photographic sound recording means comprising; a uniformly movablephotosensitized film; a rectilinear light source; a cylindrical mirror,vibratile to sound, adapted to reflect an attenuated image of saidsource; and a lens intermediate said mirror and said film, whereby anattenuated secondary image of the first said image may be projected uponsaid film transversely to its direction of motion.

3. Photographic sound recording means com rising; a uniformly movablephotosensltized film; an illuminable rectilinear filament of greattenuity; a cylindrical mirror, vibratile to sound, adapted to reflect anattenuated image of said filament; and a lens intermediate said mirrorand said film, whereby an attenuated secondary image of the first saidimage may be focused upon said film transversely to its direction ofmotion.

4. Photographic sound recording apparatus comprising; a uniformlymovable photo-sensitized film; an illuminable recti linear filament; acylindrical mirror, vibratile to sound in a plane parallel to the film,adapted to reflect an attenuated image of said filament; a lensintermediate said mirror and said film, whereby an attenuated secondaryimage of the first said image may be focused 'upon said filmtransversely to its direction of motion; and telephonic means forvibrating said mirror.

5. Photographic sound recording apparabe focused upon said filmtransversely to its direction of motion; and means for energizingsaidcoil by a telephonic current.

6. Photographic sound recording apparatus comprising; a uniformlymovable photo-sensitized film; an illuminable rectilinear filament; anintermediately pivoted armature having its extremities in constantmagnetic fields of the same flux direction, and adapted to vibrate in aplane parallel to the film; a coil surrounding said armature adapted forvariably magnetizing it; a cylindrical mirror mounted upon an extremityof the armature co-axial therewith,

' and adapted to reflect an attentuated image of said filament; a lensintermediate said mirror and said film, whereby an attenuated secondaryimage of the first-said image may be focused upon said film transverselyto its direction of motion; and means for energizing said coil by atelephonic current.

7 Photographic sound recording apparatus comprising; a uniformly'movable photo-sensitized film; an illuminable rectilinear filament;means for producing a pair of contant magnetic fields, parallel to eachother and of the same flux direction; .an intermediately pivotedarmature having its respective extremities in said fields, and adaptedto vibrate in a plane parallel to the film; a coil surrounding saidarmature adapted for variably magnetizing it; a cylindrical mirrormounted upon an extremity of the armature co-axial therewith, andadapted to reflect an attenuated image of said filament; a lensintermediate said mirror and said film, whereby an attentuated secondaryimage of the first said image may be focused upon said. filmtransversely to its direction of motion; and means for energizing saidcoil by a telephonic current.

8. Photographic sound recording apparatus comprising; a uniformlymovable photo-sensitized film;van illuminable rectilinear filament; amagnet having opposed bifurcated poles with gaps between the respective.opposed pole faces; an interme-h .and means for energizing said diatelypivoted armature having its respective extremities in said gaps, andadapted to vibrate in a plane parallel to the film; a coilsurroundingsaid armature adapted for variably magnetizing it; acylindrical mirror mounted upon an extremity of the armature co-axialtherewith, adapted to reflect an attentuated image .of said filament; alens intermediate said mirror and said film, whereby an attentuatedsecondary image of the first said image may be focused upon said filmtransversely to its direction of motion;

coil by a telephonic current.

9. The construction set forth in claim 8 in combination with means forvarying the width of the gap between opposed pairs of the magnetic polefaces.

10. The construction set forth in claim 8 in combination with; means forvarying the width of the gap between opposed pair of the magnetic polefaces; and resilient packing between the armature and pole faces wherebythe armature is prevented from contacting with the polefaces and itsvibratory movements are damped.

11. Photographic sound recording apparatus comprising; a rotatablesprocket drum; a uniformly movable photo-sensitized film bent aroundsaid drum and engaging said sprockets; a light source; and a cylindricalmirror, vibratile to sound, whereby an attenuated image of saidsourcemay be thrown upon the portion ofthe film engaging the drum,transversely to its direction of mot-1on..

12. Photographic sound recording appa .source; and a cylindrical mirror,vibratile to sound, whereby an attenuated image of said source may bethrown normally upon the. portion of the film engaging the drum,transversely to its direction of motion.

' RUSSELL HART.

